71 lines
1.7 KiB
C
71 lines
1.7 KiB
C
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// Copyright (c) 2012-2014, The CryptoNote developers, The Bytecoin developers
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//
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// This file is part of Bytecoin.
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//
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// Bytecoin is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Bytecoin is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with Bytecoin. If not, see <http://www.gnu.org/licenses/>.
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#pragma once
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#include <unordered_map>
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#include <random>
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template <typename T, typename Gen>
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class ShuffleGenerator {
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public:
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ShuffleGenerator(T n, const Gen& gen = Gen()) :
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N(n), generator(gen), count(n) {}
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T operator()() {
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if (count == 0) {
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throw std::runtime_error("shuffle sequence ended");
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}
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typedef typename std::uniform_int_distribution<T> distr_t;
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typedef typename distr_t::param_type param_t;
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distr_t distr;
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T value = distr(generator, param_t(0, --count));
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auto rvalIt = selected.find(count);
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auto rval = rvalIt != selected.end() ? rvalIt->second : count;
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auto lvalIt = selected.find(value);
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if (lvalIt != selected.end()) {
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value = lvalIt->second;
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lvalIt->second = rval;
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} else {
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selected[value] = rval;
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}
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return value;
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}
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void reset() {
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count = N;
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selected.clear();
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}
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private:
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std::unordered_map<T, T> selected;
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T count;
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const T N;
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Gen generator;
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};
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